To pair angels it's best to buy a smaller juv. specimen than the established fish. All angels as far as I know start life as a female and will become male as the reach maturity. After QT introduce the fish into the same tank, but keep them separate so they can get close but not close enough to do any damage. After a while(month+) take out the divider and see how the two fish interact. There likely will be a little aggression at the beginning, but they should work it out quickly. Pairing fish is not always possible and generally from what I have read the best bet is to start with two small juvenile fish and let them figure out who's going to be the male. GL with your fish.